The man stripped naked, jumped into the pen and began taunting the male and female big cats, The Guardian reported.

Zookeepers first turned a hose on the animals, which had instinctively attacked the intruder. They then fired a tranquilizer dart, but it missed the lions and instead struck the man, identified by local media as 20-year-old Franco Luis Ferrada, in the neck.

As Ferrada was being mauled, a zookeeper shot the lions with live rounds. They died a short time later. Ferrada was rushed to a local health clinic, where he was in critical condition.

Santiago police said he left what's believed to be a suicide note. "We are comparing it with other [writing samples]," said sub-commissioner Gerson Sepulveda.

Critics took to social media to complain about the handling of the incident, with many condemning the zoo for killing the lions.